JPH09243662A - Manufacture of probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a probe which comprises bump contacts which restrain the nonuniformity of their shape and an irregularity in their height even when the bump contacts are formed by an electrolytic plating method. SOLUTION: A conductive circuit inside through holes 4 in an insulating substrate 1 is used as a cathode, a metal is precipitated and filled so as to protrude inside the through holes 4 by an electrolytic plating operation, and bump contacts 2 are formed. In this case, while a stirring state which stirs a plating liquid in a plating tank and a non-stirring state which stops its stirring operation are being repeated alternately. The electrolytic plating operation is performed, and the bump contacts 2 are grown. It is preferable that the breakdown in terms of time of one cycle when the stirring state and the non- stirring state are repeated alternately is 5-30sec or higher for the stirring state and 3-100min or lower for the non-stirring state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a circuit board having a bump contact which is useful for measuring various electrical characteristics of a microscopic inspection object such as an integrated circuit or for a burn-in test performed at a high temperature. .

[0002]

2. Description of the Related Art In recent years, inspection of various electrical characteristics such as burn-in test for fine semiconductor elements such as integrated circuits has been conducted.
Stage cut from silicon wafer (die level)
Therefore, it is required to be performed on a chip (bare chip) before packaging. Further, in semiconductor mounting such as CSP (chip size package), bonding with bare chip size is being performed. As described above, for conductors formed in a fine pitch in an IC chip or the like,
A circuit board having bump contacts is known as a material for repeated contact and permanent bonding. Hereinafter, the circuit board having the bump contacts will be simply referred to as a "probe" regardless of the application such as repeated contact or permanent bonding.

The bump contact is a contact formed so as to protrude from the surface of the circuit board, and generally has a dome-shaped outer diameter. A plurality of bump contacts are provided according to the object to be inspected and the object to be mounted, and each bump contact has a structure in which it is electrically connected to a specific conductive circuit of the circuit board. The circuit board having the bump contacts is used as a probe for inspection and as a film carrier for mounting an IC bare chip (see JP-A-62-182672).

As a method of forming a bump contact, a method of depositing and growing a contact material by using an electroconductive circuit as a negative electrode by electrolytic plating by a dipping method or a jet method is generally used. In the process of this electroplating, studies have been conducted to suppress abnormal deposition of bump contacts and to form bump contacts at a uniform height. For example, in order to solve the problem that irregular-shaped bump contacts grow depending on the direction of the flow of the plating solution with respect to the surface to be plated, the nozzle for ejecting the plating solution and the surface to be plated may be kept parallel and the nozzle may be two-dimensionally swung. Known (Japanese Patent Laid-Open No. 2-6
No. 1089). Further, in the method of forming bump contacts using a jet cup, it is known that bump contacts having a uniform height can be obtained by plating while floating in a horizontal posture (Japanese Patent Laid-Open No. 4-315434). See the bulletin).

[0005]

However, it is difficult to make the flow velocity and flow direction of the plating solution on the surface to be plated completely uniform, and in particular, a leveler as a smoothing agent and a brightener as a brightening agent are included. The bump contact formed by electrolytic plating is sensitive to the flow of the plating solution, and the shape of the bump contact is likely to be uneven such that the apex of the bump contact is deviated in the flow direction of the plating solution. In addition, the abnormal bump contact with uneven vertices has a lower height from the surface of the insulating substrate than a normal bump contact with no uneven vertices, and thus a contact failure in an electrical inspection or an IC chip during semiconductor mounting. Poor bonding with

An object of the present invention is to solve the above problems, and to provide a method for manufacturing a probe having bump contacts formed by electrolytic plating, in which unevenness in shape and variation in height are suppressed. It is to be.

[0007]

The probe manufacturing method of the present invention has the following features. (1) A conductive circuit is provided on one surface of an insulating substrate, a through hole is provided on the other surface of the insulating substrate at a position where a bump contact is to be formed, and a conductive circuit is provided on the inner bottom surface of the through hole. When the exposed conductive circuit exposed in the through hole is used as a cathode and electrolytic plating is performed to fill the through hole with metal and further project the bump to form a bump contact, the plating solution in the plating tank is agitated. A method for manufacturing a probe, characterized in that electrolytic plating is performed while alternately repeating a stirring state and a non-stirring state in which the stirring is stopped to grow bump contacts.

(2) When the stirring state and the non-stirring state are alternately repeated, one cycle includes a time period of 5 seconds to 30 seconds and a non-stirring state of 3 minutes to 1 minute.
The method for producing a probe according to (1) above, which is set to 00 minutes or less.

(3) Agitation of the plating solution in the plating tank is either agitation by jetting air, agitation by circulating the plating solution using a pump, agitation by movement of an agitation blade, or agitation by movement of the insulating substrate itself. The method for producing a probe according to (1) above.

(4) Controlling the temperature of the plating solution so that the temperature of the plating solution in the vicinity of the conductive circuit exposed in the through hole has a temperature difference of 2 degrees or less between different through holes. The method for producing a probe according to (1) above.

(5) By further providing heating means for heating the plating solution all around the plating tank and controlling the temperature difference between the respective parts of the heating means to within 1 degree, the temperature of the plating solution can be controlled. The method for producing a probe according to (4) above, which is controlled.

(6) The heating means is a closed type heating tank that surrounds the entire plating tank, and the inside of the channel provided in the wall surface of the heating tank is heated by an external heat source. The method for producing a probe according to (5) above, wherein

The probe of the present invention is not only a probe for making a temporary contact with an object to be contacted like a probe for inspection, but also a connection to be used while being in a permanent contact like a film carrier on which a bare chip is mounted. It also means means.

[0014]

[Function] When forming bump contacts by electrolytic plating,
A stirring state in which the plating solution in the plating tank is mechanically stirred,
By performing the plating while alternately repeating the non-stirring state in which the stirring is stopped, the distribution of the ion concentration and the temperature distribution in the plating solution can be made more uniform throughout the plating bath. As a result, even if the through holes formed in the insulating substrate are distributed over a wide range on the substrate surface, the bump contacts formed in each through hole have a uniform shape and contact height. There will be less variation. The bump contact height is the height of the top portion of the bump contact relative to the surface of the substrate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Here, the manufacturing method of the present invention will be described by taking as an example the case of the structure of a probe for inspection for contacting an electrode pad of an IC to perform an operation inspection.

FIG. 1 is a view showing an example of a bump contact forming step in the manufacturing method of the present invention, showing a state in which the bump contact is formed by electrolytic plating. As illustrated in the figure, a conductive circuit 3 is provided on one surface of the insulating substrate 1, and a through hole 4 is provided on the other surface of the insulating substrate at a position where a bump contact is to be formed. The conductive circuit 3 is exposed on the inner bottom surface of the, the conductive circuit exposed in the through hole 4 is used as a cathode, and the metal is deposited and filled in the through hole by electrolytic plating to form a conductive path. And bump contact 2 by protruding from the surface of the insulating substrate.
And form a probe. Further, 7 is a plating solution, 8 is a plating tank, and 9 is an anode. In this electrolytic plating step, while alternately repeating a stirring state of stirring the plating solution and a non-stirring state of stopping the stirring,
Grow bump contacts.

In the example shown in FIG. 1, the plating solution is agitated by circulating the plating solution through a filter (not shown) by the pump 10. Further, the plating tank 8 is further housed in a heating tank 12 and is closed by a heating tank lid 13. A heating medium circulates between the heating tank and the wall of the heating tank lid with an external heat source, and indirectly heats the plating solution to a constant temperature via the wall surface of the plating tank. The temperature control of the plating solution 7 is performed by controlling the heater by the temperature sensor 11 immersed in the plating solution 7.

The probe obtained in the example of FIG. 1 has a plurality of bump contacts 2 formed on one surface side of the insulating substrate 1,
The conductive circuit 3 formed on the other surface of the insulating substrate,
The insulating substrate has a basic structure in which the metal 5 filled in the through hole 4 provided in the thickness direction of the insulating substrate is electrically connected. In the example of the figure, the conductive circuit is further provided with an insulating film 6.
Covered by

The material of the insulating substrate is a conductive circuit,
There is no particular limitation as long as it stably supports the bump contacts and has substantially electrical insulating properties. Further, in order to allow the bump contact to flexibly follow and contact the contact target portion, a flexible material is preferable. Examples of such materials include polyester resins, epoxy resins, urethane resins, polystyrene resins, polyethylene resins, polyamide resins, polyimide resins, acrylonitrile-butadiene-styrene (ABS) copolymer resins, polycarbonate resins. Thermosetting resins or thermoplastic resins such as resins, silicone-based resins, and fluorine-based resins are mentioned. Among them, polyimide-based resins, which are excellent in heat resistance, dimensional stability by heating, and mechanical strength, are particularly preferably used. It

The conductive circuit is not limited to the wiring pattern,
It is a broad concept that includes electrodes and leads. The material of the conductive circuit is not particularly limited as long as it is a material having conductivity, but the material of the circuit pattern in a known circuit board is preferable, and in particular, the wiring width becomes finer with the fine pitch of the contact target portion. Decrease,
Copper, which has low resistance, is preferable because it requires a high-speed signal. The thickness of the conductive circuit is not particularly limited,
It is preferable to set the thickness to 1 μm to 200 μm, preferably 5 μm to 80 μm.

The method of forming the conductive circuit on one surface of the insulating substrate includes a method of forming the insulating substrate by electroless plating, sputtering or the like, or a conductive circuit such as a copper foil having a varnished insulating substrate. There are a method of forming by coating and curing, and a method of bonding a film-like conductive circuit and an insulating substrate with an adhesive agent.

The conductive circuit may be further covered with an insulating film. That is, the conductive circuit is sandwiched between the insulating substrate and the insulating film layer. The material of the insulating film may be any material as long as it has electrical insulation. When this insulating film is used as a product as it is, it is preferable to use the same material as the insulating substrate, which causes the linear expansion coefficient of the insulating substrate and the insulating film to be equal and curls due to temperature changes. Disappears. Further, if this insulating film is used as a primary resist film for electrolytic plating, a known resist film material may be used, and it can be easily peeled off after electrolytic plating, and there is no current leakage during electrolytic plating. Those are preferable. In particular, a heat resistant vinyl chloride resist is preferable because it can be mechanically peeled by adjusting the plasticizer without current leakage. The method of laminating the conductive circuit and the insulating film is also
Similar to the case of the conductive circuit and the insulating substrate, a vinyl chloride resist can be applied by screen printing.

The method of forming the through holes in the insulating substrate includes mechanical punching method such as punching, photolithography processing, plasma processing, chemical etching processing, laser processing and the like. Is preferably laser processing capable of fine processing, and it is particularly preferable to use perforation processing using an ultraviolet laser having an oscillation wavelength in the ultraviolet region. The shape of the opening of the through hole, that is, the shape of the cross section perpendicular to the longitudinal axis of the through hole is not limited, but a circular shape is preferable. The diameter of the through hole is φ5μm
To φ200 μm, particularly preferably about φ8 μm to φ100 μm.

The metal material filling the through holes and the metal material forming the bump contact are not particularly limited as long as they can be deposited by the electrolytic plating method, and known metal materials can be used. For example, gold, silver, copper, platinum, lead,
Single metals such as tin, nickel, cobalt, indium, rhodium, chromium, tungsten, and ruthenium, or various alloys containing these as components, such as solder, nickel-tin, and gold-cobalt.

The current efficiency is preferably 90% or more. 90%
If it is less than the above range, a large amount of gas is generated together with the deposition of metal, so that it is difficult to form bump contacts.

Watt bath containing a brightener as a plating solution,
When using a sulfamic acid bath, the concentration of Cu impurities is preferably 5 ppm or less. If it exceeds 5 ppm, the apex of the bump contact becomes recessed, the height from the surface of the insulating substrate to the apex of the bump contact becomes low, and contact failure occurs, which is not preferable.

The structure of each bump contact is as follows.
After forming a bump contact serving as a core using a metal material that is a good conductor and is inexpensive, such as copper or nickel, the surface of the bump contact is made of a metal of high hardness or a material that is stable in terms of material, depending on the application. A film (surface layer) may be provided. Such noble metals include various noble metals. For example, it is preferable to use gold, which is chemically stable and has high contact reliability, for joining to a semiconductor element, and rhodium, ruthenium, or the like having high hardness for electrical inspection such as burn-in.

Although the height of the bump contact is not particularly limited, it is preferably about 1 μm to 100 μm. However, this value is a nominal dimension of the height of the bump contact, and the height of the bump contact formed on the same insulating substrate has a variation in height regardless of the nominal dimension. Ideally it should be zero. In actual use, the height variation of the bump contact may be within ± 2 μm, but the tolerance range of the variation may be set freely according to the application.

The stirring state is a state in which the stirring means operates and the plating solution is forcibly stirred. Means for putting the plating solution in a stirring state is not limited, for example, stirring by jetting air, stirring by circulating the plating solution using a pump, stirring by movement of a stirring blade, stirring by movement of the insulating substrate itself, Other examples include stirring by vibration of the plating tank itself. When stirring is performed by circulating the plating solution using a pump, the total bath amount in the plating tank is preferably 0.1 rotations or more and 1 rotation or less. Here, one rotation means, for example, if the total amount of the bath in the plating tank is 10 liters, 10 liters are circulated per minute. Therefore, the circulation amount of the liquid per minute is determined by the amount of the plating liquid put in the plating tank. If it is less than 0.1 rotation, it is difficult to make uniform the ion concentration and temperature of the plating solution generated during the non-stirring state, and if it is more than 1 rotation, it takes a long time to return to the non-stirring state and deforms along the flow of the plating solution. Bump contact is generated, which is not preferable.

The time for which the stirring state is continued is as follows:
It is preferably 5 seconds or more and 30 seconds or less, and particularly preferably 10 seconds or more and 20 seconds or less.

The non-stirred state means a state in which the operation of the stirrer is stopped, and includes a state in which the plating solution is flowing due to the inertia of the stirrer after the stirring is stopped. After the flow due to the inertia of the plating solution is stopped, the migration of metal ions due to the electric field, the diffusion of metal ions due to the concentration difference, the convection of the plating solution due to the temperature difference, etc. are Has occurred in. The time for which the non-stirred state is continued is preferably 3 minutes or more and 100 minutes or less per time. If the duration of the non-stirred state is less than 3 minutes, the bump contact is deformed along the flow of the plating solution, which is not preferable. Further, if the non-stirred state exceeds 100 minutes, the ionic concentration and temperature of the plating solution will vary, which makes the bump contact height non-uniform, which is not preferable.

The current value in electrolytic plating is 0.01 m
A range of A or more and 100 mA or less is preferable, and other than this range, the ion concentration becomes too small, gas is generated, and abnormal precipitation occurs, which is not preferable.

It is preferable that the temperature of the plating solution near the conductive circuit exposed in the through hole has a temperature difference of 2 degrees or less between different through holes. If this temperature difference exceeds 2 degrees, the amount of precipitation varies and it is not preferable.

As a preferable example for keeping the temperature difference within 2 degrees, heating means for heating the plating solution is further provided all around the plating tank, instead of locally heating the plating solution. It is preferable to indirectly heat the plating solution by heating it through the wall surface of the plating tank. In particular,
By controlling the temperature difference between the respective parts of the heating means within 1 degree, it becomes easy to control the temperature of the plating solution within 2 degrees. Examples of the heating means include a structure in which a large number of heaters are evenly dispersed over the entire wall surface of the plating tank. As shown in FIG. 1, the plating tank 8 is further housed in a heating tank 12 and a heating tank lid is provided. A preferable heating means is a structure which is covered with 13, and a heating medium is circulated between the heating tank and the wall of the heating tank lid with the external heat source 14. The heat medium may be water, oil, steam or the like that can control the temperature.

The plating bath is not limited as long as it has a good thermal conductivity and is insulated, but a stainless steel coated with Teflon is preferable. The temperature control of the plating solution is preferably performed by disposing a temperature sensor in the plating solution. Any number of temperature sensors may be used as long as they do not disturb the current distribution during plating, but it is preferable to set a large number of temperature sensors because fine adjustment of the temperature is possible.

Current capacity is 0.01 mA / liter or more 1
It is preferably less than or equal to 00 mA / liter, and if less than 0.01 mA / liter, power supply varies due to electric leakage from the insulating substrate. On the other hand, if it exceeds 100 mA / liter, the supply of ions in the non-stirred state will be insufficient, resulting in abnormal deposition of bump contacts, which is not preferable.

The current density is 1 A / dm ² or more and 10 A / dm ^2.
It is preferably ² or less. Current capacity is less than 1 A / dm ²
When it is set to mA / liter or less, the variation of precipitation becomes large, while when it exceeds 10 A / dm ² , the variation becomes large when the current capacity is set to 1 mA / liter or more, which is not preferable.

The posture when the insulating substrate is placed in the plating solution in the plating bath is such that the angle between the surface of the insulating substrate on the side where the through holes are opened and the vertical direction is ± 20 °. Is preferred. If this angle is not within the range of ± 20 °, and if the opening of the through hole faces downward, the bubbles present in the plating solution adhere to the through hole and the bump contact grows along this. It is not preferable because it is defective in appearance. Also, if the opening of the through-hole faces upward, foreign matter of organic or inorganic components floating in the plating solution fills the through-hole,
The plating cannot be deposited, or even if it is deposited, the shape of the bump contact becomes abnormal, which is not preferable.

[0039]

The present invention will be specifically described below with reference to examples. Example 1 A copper foil having a thickness of 35 μm was coated with a polyimide precursor solution so that the thickness after drying was 25 μm, dried, and cured to form a two-layer film of a copper foil and a polyimide film as an insulating substrate. It was made. Next, after forming a resist layer in a circuit pattern on the surface of the copper foil, a conductive circuit having a desired circuit pattern was formed using a photo process.

The polyimide film is irradiated with KrF excimer laser light having an oscillation wavelength of 248 nm through a mask from the rear surface of the surface where the conductive circuit is formed to the position where the bump contact is to be formed, and dry etching is performed to penetrate the polyimide film. 1800 holes were formed and the conductive circuit was exposed on the inner bottom surface of each through hole. The bottom diameter of each through hole was 50 μm, and the opening diameter was 60 μm. Next, oxygen plasma was applied to the through-holes, and a heat-resistant vinyl chloride resist was screen-printed on the conductive circuit on the side opposite to the polyimide to a thickness of 50 μm, and dried.

After UV irradiation, the copper foil exposed in the through-holes of the two-layer base material was subjected to ultrasonic waves of 40 kHz using a sodium persulfate-based soft etching solution to have an electric conductivity of 2 μS / cm or less. After washing with water, the anode 7 is used as an anode, the conductive circuit is used as a cathode, and nickel is deposited and filled as a contact material in the through hole, as shown in FIG.
Further, the bump contact 2 was formed by growing so as to project from the surface of the insulating substrate. The plating conditions are as shown below.

[Plating conditions] The components of the plating solution are nickel sulfate; 300 as components in 1 liter of the plating solution.
g, nickel chloride; 65 g, boric acid; 45 g, additive (manufactured by Ebara-Udylite Co., Ltd.) # 610; 15 ml, # 6
3; 20 ml, # 62; 5 ml. The operating conditions for electrolytic plating are: plating solution amount: 10
L, plating temperature; 60 ° C. ± 0.5 ° C., current density 4.5 A / dm ² . The current value was continuously changed with the passage of time. The current value at each elapsed time is shown below. (Elapsed time / current value) = (0 minutes / 1.59 m
A), (25 minutes / 2.28 mA), (30 minutes / 2.85)
mA), (35 min / 3.46 mA), (40 min / 5.4
0 mA), (45 min / 7.76 mA).

The non-stirred state was 10 minutes, and the stird state was 1
It was set to 0 seconds. The stirring capacity was 0.5 rotation circulation.

The specifications of the plating tank are 30 cm × 30 cm ×
It was 30 cm (depth). The entire plating tank is further housed in a closed type heating tank, and the inside of the flow path provided in the wall surface of the heating tank uses water as a heat medium at 60 ° C. in each part of the flow path.
Circulate while controlling the temperature to be ± 0.2 ° C,
The plating solution was uniformly heated through the wall surface of the plating tank.
The temperature sensors were installed at the center of the plating tank and at the eight corners. The distance between the cathode and the anode was 20 cm.

The agitating means is such that the plating solution is circulated by a pump, sucked from the lower side of the object to be plated and discharged from the lower side of the anode into the tank to circulate the plating solution.

The formed bump contact had a shiny mushroom shape, and the apex of the bump contact was located at the center of the bump contact diameter, and no abnormality was observed. The bump contact height from the polyimide surface is 20 μm on average, and the width of height variation is 3 μm (minimum height 18 μm, maximum height 21 μm.
m).

Comparative Example 1 A bump contact was formed under the same conditions as in the above-mentioned example except that the non-stirred state was 2 minutes. As a result, the bump contacts were deformed along the flow direction of the plating solution, the bump contact height was 18 μm on average, and the height variation width was 7 μm (minimum height 13 μm, maximum height 20 μm).
The average height is lower than the bump contact formed in
The width of height variation was more than doubled.

Comparative Example 2 Except that the temperature of the plating solution in the vicinity of the cathode (the conductive circuit exposed in the through hole) on the insulating substrate was 58 ° C. to 62 ° C., and the temperature difference was 4 ° at maximum. Formed bump contacts under the same conditions as in the above example. As a result, when the temperature of the cathode surface was set to about 58 ° C., the average height of the bump contacts was 18 μm. On the other hand, when the temperature was around 62 ° C., the average height of the bump contacts was 22 μm. As a whole, the average height of the bump contacts is 20 μm, and the width of height variation is 7 μm (minimum height 16 μm,
The maximum height was 23 μm, and the average height was the same as that of the bump contact formed in Example 1, but the range of height variation was more than double as in Comparative Example 1.

[0049]

When the bump contact is grown by the electrolytic plating method, the contact material is deposited while alternately repeating the stirring state and the non-stirring state, whereby the variation in the height of the bump contact can be suppressed. . At the same time, it is possible to prevent the shape of the bump contact from being abnormal.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a method for producing a probe of the present invention.

[Explanation of symbols]

 1 Insulating Substrate 2 Bump Contact 3 Conductive Circuit 4 Through Hole 5 Metal (Contact Material) 6 Insulating Film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Yada 1-2-1, Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (6)

[Claims] 1. A conductive circuit is provided on one surface of an insulating substrate, a through hole is provided on the other surface of the insulating substrate at a position where a bump contact is to be formed, and a conductive circuit is formed on the inner bottom surface of the through hole. When the circuit is exposed and the conductive circuit exposed in the through hole is used as a cathode, the through hole is filled with a metal by electroplating and further projected to form a bump contact. A method of manufacturing a probe, characterized in that electrolytic plating is performed while alternately repeating a stirring state of stirring and a non-stirring state of stopping the stirring to grow bump contacts. 2. The time sequence of one cycle when the stirring state and the non-stirring state are alternately repeated is that the stirring state is 5 seconds to 30 seconds and the non-stirring state is 3 minutes to 100 minutes.
The method for producing a probe according to claim 1, wherein the amount is not more than a minute. 3. The stirring of the plating solution in the plating tank is any one of stirring by jetting air, stirring by circulating the plating solution using a pump, stirring by movement of a stirring blade, and stirring by movement of the insulating substrate itself. The method for producing a probe according to claim 1, wherein 4. The temperature of the plating solution is controlled so that the temperature of the plating solution near the conductive circuit exposed in the through hole has a temperature difference of 2 degrees or less between different through holes. A method for manufacturing a probe according to claim 1. 5. The temperature of the plating solution is controlled by further providing heating means for heating the plating solution all around the plating tank, and controlling the temperature difference between respective parts of the heating means to within 1 degree. The method for producing a probe according to claim 4, wherein the probe is produced. 6. The heating means is a hermetically sealed heating tank that surrounds the entire plating tank, wherein a heating medium heated by an external heat source is provided in a flow passage provided in the wall surface of the heating tank. The method for producing a probe according to claim 5, wherein the probe is circulated.